The Americans with Disabilities Act of 1990 (ADA) is a law that was enacted by the U.S. Congress in 1990. It was signed into law on July 26, 1990, by President George H. W. Bush, and later amended with changes effective January 1, 2009.

The ADA is a wide-ranging civil rights law that prohibits, under certain circumstances, discrimination based on disability. It affords similar protections against discrimination to Americans with disabilities as the Civil Rights Act of 1964, which made discrimination based on race, religion, sex, national origin, and other characteristics illegal. Disability is defined by the ADA as "a physical or mental impairment that substantially limits a major life activity." The determination of whether any particular condition is considered a disability is made on a case by case basis. Certain specific conditions are excluded as disabilities, such as current substance abuse and visual impairment which is correctable by prescription lenses.

The "original intent" of the law, as co-conceived by Lex Frieden and Mitchell J. Rappaport, was to create civil rights law protections for people with disabilities that would be permanent, would not be able to be reversed or weakened, and would prohibit all discrimination. It was also intended so that Americans with disabilities would be kept in the mainstream in terms of scientific and medical research and developments, especially opening future opportunities in Space exploration to them, as well as public policy changes, healthcare law and policy changes, and civil rights protections and public law changes for Americans with physical, mental and cognitive disabilities. It was intended to be a flexible set of laws that could only be strengthened, not weakened, by future case law.

Americans with disabilities comprise one of the largest minority groups in the United States. According to the Disability Status: 2000 - Census 2000 Brief approximately 20% of Americans have one or more diagnosed psychological or physical disability:

Census 2000 counted 49.7 million people with some type of long lasting condition or disability. They represented 19.3 percent of the 257.2 million people who were aged 5 and older in the civilian non-institutionalized population -- or nearly one person in five..."

This percentage varies depending on how disabilities are defined. According to Census Brief 97-5, "About 1 in 5 Americans have some kind of disability, and 1 in 10 have a severe disability."

Although Americans live in the only industrialized nation without universal healthcare^{[citation needed]}, those with disabilities can generally find adequate levels of subsidized support from a variety of sources, generally at the regional level. While most rural areas — especially in the Great Plains region — have little or no government-organized medical support infrastructure for the permanently disabled indigent population, most major urban centers have healthcare systems. One of the largest developed systems is the Harris County Mental Health and Retardation Authority (MHMRA).^{[citation needed]} Started in 1992 as a spinoff of the local University of Texas Health Science Center, MHMRA proved to be a success as it focused on handling complex Medicare and Medicaid paperwork for patients, in a system which greatly cut down on administration costs and sped the approval process.

Americans, or American people, are the citizens of the United States of America. The country is home to people of different national origins. As a result, Americans do not equate their nationality with ethnicity, but with citizenship. Aside from the Native American population, nearly all Americans or their ancestors immigrated within the past five centuries.

Despite its multi-ethnic composition, the culture held in common by most Americans is referred to as mainstream American culture, a Western culture largely derived from the traditions of Western European immigrants. It also includes influences of African American culture. Westward expansion integrated the Creoles and Cajuns of Louisiana and the Hispanos of the Southwest and brought close contact with the culture of Mexico. Large-scale immigration in the late nineteenth and early twentieth centuries from Southern and Eastern Europe introduced a variety of elements. Immigration from Asia, Africa, and Latin America has also had impact. A cultural melting pot, or pluralistic salad bowl, describes the way in which generations of Americans have celebrated and exchanged distinctive cultural characteristics.